1. Field of the Invention
The present invention relates to a method of treating at least the surface of unvulcanized and therefore tacky elastomeric semi-finished products for use in further manufacturing, or molded objects, with a powdery or dust-like separating material which neutralizes the tackiness.
The surfaces of the unvulcanized elastomeric molded objects and semi-finished products are tacky. On the one hand for reasons of good bonding action, this is desirable for subsequent treatment. Thus, for example, if semi-finished products are to be bonded with other such products, or are to be built-up one upon the other, before being polymerized or vulcanized, such tackiness is desirable.
On the other hand, this tackiness is undesirable and disruptive if such semi-finished products are to be temporarily stored, packaged, or transported prior to being bonded and vulcanized with other parts.
Furthermore, certain problems exist in the region of the production molds with regard to venting, molding, and removal from the molds if these elastomeric molded obJects and semifinished products are to be vulcanized.
2. Description of the Prior Art
In order to neutralize the tackiness, various separating materials have been used for many years in order to treat and thus neutralize the tacky surfaces.
It is known to coat or dust the tacky surface with dissolved carbon black, with corn meal, or with zinc stearate.
It also is known to dust the tacky surface with rubber powder, especially for the perforated side panels in the retreading of vehicle tires. Tacky surfaces are furthermore powdered with hard rubber dust or coarse powder. Such powdery or dust-like separating material is obtained by roughing and grinding rubber parts during tire retreading. See Austrian Pat. No. 293 902, and German Pat. Nos. 19 43 876 and 818 419.
The common aspect of the heretofore known powdery or dustlike separating materials for neutralizing tackiness is that these materials are fine particles of a vulcanized and cured rubber product. The chemical and physical properties differ considerably, at least in part, from those of a nonvulcanized elastomeric part, for example, the purity is non-uniform, the granular sizes and the consistency differ from that of unvulcanized parts. Furthermore, powder from vulcanized rubber is, to a certain extent, foreign matter relative to the nonvulcanized elastomeric molded object or the elastomeric semi-finished product to which powdery rubber is to be applied.
Any form of foreign matter relative to the elastomers should be avoided, because the homogeneity of a product made of any desired elastomer is adversely affected thereby when it is to be polymerized or vulcanized.
An object of the present invention is to improve the method of treating a tacky elastomeric surface in such a way that not only is the tackiness neutralized, but the quality of the bond between the elastomeric molded object or semifinished product and an elastomeric molded part which is not polymerized, or a molded rubber part, is improved; the bond should be more homogeneous.
In addition to the neutralization of the tackiness, and the improvement of the quality of the bond, a further object of the present invention is that a smaller quantity of separating material will suffice in comparison to the heretofore known materials and measures.